megabuddys

I am replacing a 5.3 with a 6.0 and need some guidance on what compression ratio to shoot for. This vehicle is already built, I had something let go in the bottom end of the 5.3.

4100lb 4wd vehicle, 3.73 with 29 inch tall tires.
78/75 on3 turbo
w2a intercooler system.

Premium Pump gas, NO METH. 15-18lbs boost. MAX.

Currently building a 6.0/ .030 so 370 cube,
k444x3 pistons with the -11 cc dish, so I can taylor my final compression ratio with whatever head needed. LS9 Gaskets probably.

Isky Triple 12 cam.

I have 799 heads and 317's

So the question is 9.1 ish or 9.6 ish Compression ratio.
799's = 9.6 ish
317's = 9.1 ish

I only run premium pump gas and No meth. Please advise.

Vortec350ss

iTrader: (20)

With that much boost and 93 only you may be forced to run the 317's and target 9.0ish. Even still 15-18psi may be more than it can handle on pump gas.

to put it in prospective the LSA/LS9/LSX376B15 are all about 9.0 compression.

George C....

all depends on how you set the vehicle up, i just finished up a ls3 which is 11.0 on 16 psi on straight 93

be smart with AFR and timing and should be fine but make sure the combo itself isnt a cluster ****

and my daily is 10.25 cr and sees 12 psi with 12* timing on straight 93

smokeshow

iTrader: (16)

If you find yourself fuel/octane limited, go lower compression. Less picky in the tune as it's not as easy to damage the engine, and it will make more power.

Vortec350ss

iTrader: (20)

I'd love to see that timing table lol

megabuddys

I am limiting the combo to Premium fuel only. I don't want to deal with the headaches with E85 and I want to fuel up anywhere without worry. I would have to upgrade injectors probably too. Currently have 60's @ 64% @ 58psi. (11 psi boost)

I am gaining 45 cubic inches, so driveability wont be an issue, combined with the somewhat docile Triple 12 cam. So the lower compression wont kill the set up by any means. I just don't know, its a lot of work to swap heads, I would rather not guess as to which compression to shoot for.

Keep the suggestions coming. 9.2 or 9.6 "ish" ratio ??

George C....

8* it made 744 at 13* it made 806

tuned off plugs, could of took another degree based on strap

br7ef plugs

also using IAT retard to keep motor safe


dont need alot of timing when you have compression

George C....

9.5 is ideal for most street motors that will see modest boost

if you are limited to boost then compression helps...

Atomic

iTrader: (42)

I would shoot for around 9:1

iDEALS1

iTrader: (10)

I am running 10.4:1 with 93, but I will run meth too. We will see how well it works.